This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:
CA carrier aggregation
CC component carrier
DL downlink
DwPTS downlink pilot time slot
eNode B enhanced Node B (also, eNB)
FDD frequency division duplex
HetNet heterogeneous network
GHz giga-Hertz
GP guard period
LTE long term evolution
LTE-A long term evolution advanced
OFDM orthogonal frequency-division multiplexing
PCC primary component carrier
PDCCH physical downlink control channel
PDSCH physical downlink shared channel
PRB physical resource block
PSS primary synchronization signal
PUSCH physical uplink shared channel
Rel-8 Release 8
Rel-10 Release 10
SCC secondary component carrier
SC FDMA single carrier, frequency division multiple access
SF subframe
SSS secondary synchronization signal
TDD time division duplex
UE user equipment
UL uplink
UpPTS uplink pilot time slot
In the communication system known as evolved UTRAN (E UTRAN, also referred to as UTRAN-LTE, E-UTRA or 3.9G), the LTE Release 8 (Rel-8) is completed, the LTE Release 9 (Rel-9) is being standardized, and the LTE Release 10 (Rel-10) is currently under development within the 3GPP. In LTE, the downlink access technique is OFDMA, and the uplink access technique is SC-FDMA, and these access techniques are expected to continue in LTE Release 10.
Further releases of 3GPP LTE are targeted towards future IMT-Advanced systems, referred to herein for convenience simply as LTE-Advanced (LTE-A) which is expected to be part of LTE Rel-10. LTE-A is expected to use a mix of local area and wide area optimization techniques to fulfill the ITU-R (International Telecommunication Union Radiocommunication Sector) requirements for IMT-Advanced (International Mobile Telecommunications-Advanced) while keeping backward compatibility with LTE Release 8. Topics that are included within the ongoing study item include bandwidth extensions beyond 20 MHz, relays, cooperative MIMO and multi-user MIMO, and single user MIMO on the uplink.
LTE-A aims to provide significantly enhanced services by means of higher data rate and lower latency with reduced cost. Carrier Aggregation (CA) is one of key technologies to improve the data rate. The basic idea of CA is that LTE-Advanced terminals supporting CA can receive/transmit on multiple component carriers (CC) at the same time, thus having support for large bandwidth. It has been agreed that up to 5 (five) CCs could be aggregated in LTE Rel-10 in both FDD and TDD systems.
In Rel-10, the current discussion is mainly about CA of either FDD-FDD systems or TDD-TDD systems. However, if one operator has both TDD and FDD bands, the CA scenario of TDD/FDD is likely to become relevant. This is likely to be considered in Rel-11 and further releases. By using TDD/FDD CA, one can achieve some valuable benefits such as: balancing the traffic load among FDD and TDD systems, improving the peak data rate, and thus improving the spectrum efficiency in general for the operator.
In Germany, the government had an LTE spectrum auction this year for the 2.6 GHz spectrum. After the auction, the FDD UL/DL and TDD band is shared by four operators in a discontinuous manner. In the TDD spectrum, there is a very high chance some operators will operate with TDD system, but may still wish to support FDD UEs in case load is low in TDD system, especially in the early phase of implementation. On the other hand, an operator may also wish to have the flexibility of support TDD UE in FDD system in case of load balancing, or to improve peak data rate.